2001 Jeep Cherokee, won't start up. There is power because the radio and lights are on but turning the key over it makes a knocking sound??

Knocking Or Clicking? If It Is Making A Clicking Sound Then It Could Be Your Altenator Or Starter, If Its Not A Repeated Clicking Sound Then It Is Your Distributor. Those Are Just The Main Things

Thank you integra-b18, this helps :)

Alternator does not start the vehicle. A click could be a bad starter; a repeated click could be a weak battery. Sometimes they will turn on the lights/radio/etc, but the battery is too weak to actually start the vehicle.

Ok Take Your Altenator Out Then Try To Start Your Car Then Tell Me The Altenator Is Not The Most Important Component To Starting A Vehicle. Ha Ha The Altenator Is What Distributes The Charge Throuought The Engine. And If It Was The Battery Then All Of His Lights Would Dim When He Attemoted To Start It Then Would Finally Go Dead So Its Not The Battery. These Are Not Lego Cars Jeep Is One Of The Most Complicated Engines To Work On Aside From Bmw And Mercedes Jaguar... Etc.

Ok Take Your Altenator Out Then Try To Start Your Car Then Tell Me The Altenator Is Not The Most Important Component To Starting A Vehicle. Ha Ha The Altenator Is What Distributes The Charge Throuought The Engine. And If It Was The Battery Then All Of His Lights Would Dim When He Attemoted To Start It Then Would Finally Go Dead So Its Not The Battery. These Are Not Lego Cars Jeep Is One Of The Most Complicated Engines To Work On Asside From Bmw And Mercedes Jaguar... Etc.

You could not be more wrong. The alternator & battery work together to charge the motor; this is why you disconnect the battery when servicing the alternator, to ensure that it doesn't short out when you reconnect it. The alternator does nothing to actually start the vehicle; why do you think it's referred to as a "generator?"

As for the battery, it very well could be the issue. If the OP continues to try to start the vehicle, then they will drain it down. I've replaced dozens of batteries that were just strong enough to turn on the lights but too weak to turn over the motor.

And where are you getting this nonsense from that Jeeps are complicated? Jeep is not anymore complicated than Ford or GM.

Haha man a ricer would say that, this8384 your prob right but I'm going to need more than that, does it click or knock, will it crank at all does it sputter and run at all, can u hear the fuel pump cycle on and off with the key in the on position? Try and put a jump pack or something on it and see if it starts.

Just to clarify - the rate on INTEGRA-B18 was supposed to be "Disagree", vehmently "Disagree"...

Sounds like a sticky starter or worn selinode(sp).Try hitting the started with a small ball pean hammer,not to hard though,just tap it.If your battery is fully charged you don't need the altenator on to run the vehical,altenator is there to charge the battery when it signals low voltage from the regulator ;).After the battery is fully charge from the altenator it will kick out and not charge until it gets the signal from the voltage regulator to charge again,just wanted to clear that up :)